#include <iostream>

using namespace std;
class Singleton
{
public:
    static Singleton& get_instance();
    void get_version_flag();
    void set_version_flag(int num);
private:
    Singleton()
    {
        
        std::cout<<"Singleton()"<<std::endl;
    }
    ~Singleton()
    {
        std::cout<<"~Singleton()"<<std::endl;
    }
    int version = 0;
};